Subscriber&#39;s station for telephone systems



Patented July 1, 1947 UNITED STATES PATENT OFFICE 7 2,423,127sonsonrnnias STATION FoRTELEP'HoNE 'SYSTEMS Clement. M. Theillaumas,Lyon, France, assig-nor to International Standard Electric Corporation,New York, N. Y.,-a corporation of Delaware '10 Claims.

The present invention relates to telephone system and more particularlyto the circuitslor a subscribers telephone station in rural or othertelephone systems with manual or semi automatic service.

One object of the invention is to provide a manually operated orsemi-automatic systemineluding, a subscribers telephone station whichcontains neither a calling magneto nor a local supply battery for thetransmitter microphone.

Another object of the invention-is to provide telephone systems of thetype described including subscribers station circuits insuring properoperation of these stations with current supplied from anexc-hange.

A still further objector the invention is to provide. ina telephonesystem including a subscribersstation without magneto or battery,effective means for calling an exchange or another subscriber.

Still a further object of the invention is to pro vide" means wherebythe mechanism at asubscribersstation for calling an exchange or an othersubscriber without magneto or battery is prevented from interfering withthe proper op eration of'the ringer at the subscribers station uponreception of an incoming cal-1.

Still-another object of the invention is to provide-a subscribersstation for manual or semiautomaticservicewhich, with regard to a considerable part of its structurmis similarto and even interchangeable with asubscribers station for full-automatic service.

These and other objects are accomplished, according to the presentinvention, by the arrange ment and combination of circuits and circuitelements-set forth in the following description, defined in the appendedclaims and illustratively exemplified intheaccompanying drawing, thesingle-figure-of which is a wiring diagramof a subscribers telephonestation according to the invention and of some of the elements at theexchange to which the subscribers station iscon nected.

Generally, in-the drawing illustrative of this in vention, allcontacts-are shown in their rest .positions. V

Thefeed battery l of -the exchange? is permanently connected to theWires a and h of the line Lover two resistances of suitable value, suchas-,;for instance,- of. 5000 ohms each. The line relay 4 is connectedacross the lime wires wand b in-lseries-with a, for. instanceelectrolyticycondenser ,5 which serves .tc-isolate the relay at from thebattery I; The condenser 4 is, thus; kept 2. charged as long i as thejunction between-the e change -B- and the subscribers-station A-remainsinactive.

The subscribersstation A contains the receiver 8 and the transmittermicrophone l inductively connected in the usualmanner by means of thetransformer 8 The ringer -9 is inserted in a circuit loop which isclosedby the lower one of the-contacts I0- of' the cradle switch when-thereceiver rests on the-cradle. This loop is inserted between the wiresaandb-through a restcontest of acallingswitch Hand it contains the usualcondense-r l 2- to protect the ring-er 9 against direct current;During;- a conversation, the ro ceiver- 6' and the transmittermicrophone l" are both connected-to-thissame restcontact'of the switchll because of the closing of the contacts I3 of the cradle switchwhichare kept open as long as the receiver rests on its cradle orsupport;

The calling device comprises a series of -condensers id'to Idassociated; respectively with pairs of double cont-act switches I l-l8;lt -fll, Zl-ZZ, which,- in their rest positions'shown, connectthecondensers-l l; l5 and-l6 in parallel to the battery lthrough asuitable resistance 23;

thus keepingsaid condensers charged.

The initiation of acall lay the subscriber=necessitatesexcitation ofthe-line relay dat the exchange B'. This result is accomplished by thedischarge "in series of th'e'condensers l4; l5 and I6 which is caused bya simultaneous switching over of all the double contact switches lT-ZZupon their (right hand) 'working contacts. This operation may be"effected by the subscriber through the operation of a specialcallingswitch control mechanism; such as'the depression ofa singlecontrolbutton for all said switches or the manipulation of a dial havinga single finger hole. The switch I I is mechanically connected with theswitches I! to 2|, so asto eliminate during the discharge ofthe-condensers M- -ifi into the line L the resistance 23 which'wouldrender the discharge current too feeble.

The calling svvitch' control mechanism may be constructed in any desiredsiiiiple manner. Since it does not form a part of the present invention,it is not shown nor described in detail.

The reception of incoming calls at the subscribers station; presupposesthe transmission from the exchange over thewires of the line L of analternating current 'of lo'w neq-uencyisueh as 16,25 or 50Pi'PLS.)with"apotentia'1 difference wnicnmsyexceeu IOUVbltS'. The'lihgei 9'isthn actuated. alternatin would be aptto cause deterioration oi theelectrolytic con densers I l-I6 formed under a much lower tension ofabout 30 volts, if it were not for the resistance 23. Moreover, thisresistance 23 gives to the leakage circuit formed by said condensers asuificiently strong impedance to prevent any interference with thenormal operation of the ringer 9.

When the subscriber takes off the receiver, either after emission orupon reception of a call signal, the contact l3 of the cradle switch isclosed, so that the transmitter microphone 1 is inserted into thesupervisory loop of the operator at the exchange B, and the microphone lis, in this manner, supplied with current over the line L from theexchange battery I. Simultaneously, the contacts are opened, thusdisconnecting the leakage circuit through the condensers I4l 6 and thealarm circuit and preventing any weakening of the talking currents.

The line relay I may be protected, instead of by means of a condenser 5,by means of a unidirectional rectifier connected in such a manner thatit passes the discharge current of the condensers I4 to 16 whileblocking the condenser charging current.

Owing to the omission at the substation of the feed battery for thetransmitter microphone and of the calling magneto, it is furtherpossible, according to the invention, to construct a subscribers stationwhich can be adapted to telephone systems with full automatic service aswell as to systems with manual or semi-automatic service. The receiver,the transmitter microphone, the induction coil and the ringer can beidentical in both cases. Only the electrolytic condensers and the springcontact combinations necessitate a different wiring. Thus, thesubscribers stations according to the invention, provide for a morecomplete standardization of the material and equipment and, moreover,each station in a fullautomatic system can be easily converted into oneof a manual or semi-automatic system according to the invention, or viceversa.

The line condensers or the rectifiers to be subsituted therefor, may beprovided in the detachable line relay block of a standardizedsemi-automatic exchange installation. For this purpose, the condensersor rectifiers are inserted into a flat casing mounted on the collapsiblerear Wall of the relay support; This requires only a small modificationin the wiring on the inside and no change at all in the outside wiring.

It should be noted that the introduction of a subscribers station of thetype set forth above into a telephone network with manual orsemiautomatic service makes it necessary to hold the wire linespermanently under a current supplied by the exchange battery. However,this permanent application of current has no detrimental efiect upon theinsulation of the line, because the potential difierence of the supplybattery I does not exceed 30 volts at the end of the charge, whereas, ifa call signal is generated by the usual magneto the peak tensions mayexceed 200 volts. On the other hand, a high resistance 2, 3 is provided,in the present arrangement, between each terminal of the battery I andthe corresponding line wire. Thus, even in the case of a short circuitof the line directly outside of the exchange, the permanent maximum loadis less than 3 milliamperes, which is practically negligible. Finally,since the supervision is usually effected by means of a loop at thesubscribers station, no danger is involved in introducing into said loopthe transmitter microphone 1 to replace a dead resistance.

It will be understood that the invention is not limited to theembodiment shown and described but may be modified or varied in numerousways within the scope of the following claims.

I claim:

1. A telephone system comprising an exchange, a subscribers station,line wires connecting the exchange with the subscribers station, asupply battery connected across the line wires at the exchange, circuitsat the subscriber station including an operator's supervision loop, anda transmitter microphone inserted in said supervision loop, so as to besupplied with current from said supply battery when said supervisionloop is closed.

2. A telephone system, as claimed in claim 1, including two highresistances inserted between the terminals of said battery and thecorresponding line wires respectively.

3. A telephone system comprising an exchange, a subscribers station,line wires connecting the exchange with the subscribers station, supplybattery connected across the line wires at the exchange, a line relay tocontrol outgoing call signals connected across the line wires at theexchange, a blocking device connected across said line Wires in serieswith said relay to prevent the latter from being excited by the batterycurrent, and an energy storage circuit connected across said line wiresat the subscribers station when the latter is not busy, said storagecircuit containing at least one condenser, and subscriber controlledmeans to reverse the connection of said condenser in said storagecircuit when a. call signal is to be transmitted from said subscribersstation, said blocking means being adapted to pass current impulsesemitted from said condenser upon reversal of its connection in saidstorage circuit to permit excitation of said relay.

4. A telephone system, as claimed in claim 3, in which said storagecircuit contains a plurality of condensers normally connected inparallel with one another, and means to connect said condenser in seriesupon reversal of their connection in said storage circuit.

5. A telephone system, as claimed in claim 3, in which said condenser isan electrolytic condenser.

6. A telephone system, as claimed in claim 3, in which said subscriberstation includes a ringing circuit connected across said line wires inparallel with said storage circuit when subscribers station is not busy,said ringing circuit containing a condenser and said storage circuithaving a resistance greater than that of said ringing circuit.

7. A telephone system, as claimed in claim 3, in which said storagecircuit contains a resistance and means to short-circuit said resistanceupon reversal of the connection of said condenser in said circuit.

8. A telephone system, as claimed in claim 3, in which said subscribersstation includes a cradle switch capable of assuming a non-busy and abusy position, said cradle switch including a contact connecting saidstorage circuit to said line wires when said switch is in its non-busyposition and breaking said storage circuit when said cradle switch is inits busy position.

9. A telephone system comprising an exchange, a subscribers station, aline circuit connecting said exchange with said subscribers station, asupply battery connected across the line circuit at the exchange, a linerelay to control outgoing call signals connected across the line circuitat the exchange, a blocking device connected across the line circuit inseries with said relay to prevent the latter from being excited by thebattery current, said subscriber's station containing an operatorssupervision loop including a transmitter microphone, a receiver circuit,a ringing circuit including a condenser, and a storage circuitcontaining at least one condenser and a resistance, subscribercontrolled means at said subscribers station to reverse the connectionof said condenser in said circuit and to short circuit said resistancewhen a call signal is to be transmitted from said subscriber's station,said blocking means being adapted to pass current impulses emitted fromsaid condenser upon reversal of its connection in said storage circuitto permit excitation of said relay, and a cradle switch at saidsubscribers station capable of assuming a nonbusy and a busy position,said cradle switch in- REFERENCES CITED The following references are ofrecord in the file of this patent:

UNITED STATES PATENTS Name Date Gillette et a1 Mar. 26, 1895 Number

